Halo vs Star wars
by btrxscopez
Summary: When the combined force of the UNSC and the Covenant find a portal leading to another galaxy they send a small force into the portal and onto the other side, what is found on the other side?
1. Introduction

**Halo universe vs star wars universe**

 **This will be a story about my opinion on a conflict between the star wars universe and the halo universe and will cover the war from the beginning to the end (hopefully).**

 **( just go to the next chapter if you just want the story)**

 **However before the story begins I would like to point out the reasons some of the things I write will conflict with canon information. Firstly the force, as some will know the force doesn't affect beings from outside the galaxy, in the canon this happens when the Yuuzhan Vong invaded the star wars galaxy because of this direct force attacks (force choke ect ect) will not affect the halo universe's populous however attacks like throwing rocks at them or force lightning still work.**

 **Next is star wars weapons, we should know that star wars weapons are not actually lasers but are plasma (so are lightsabers) and these according to calculations from movie footage (link to the page at the bottom of page) travel at an average of 35m/s (the speed of a thrown baseball) which means it wouldn't be too difficult to dodge out of the way of a blaster bolt. In space it is obviously a lot faster with the fastest ones travelling at speeds of 35000m/s.**

 **I will now talk about the power of the weapons from star wars, according to Newton's 3rd of motion "every action has an equal and opposite reaction" which is represented by bullet recoil, this would also apply to star wars weapons meaning in force awakens when Han Solo shoots T8-8R with his pistol and the stormtrooper goes flying back the same thing would happen to Han Solo but it doesn't, infact there is almost no evidence of recoil at all in star wars plasma weapons leading me to believe the blaster bolts don't carry much kinetic energy but instead the damage is done by the heat made by the plasma. So essentially the star wars blaster bolts are like the covenant weapons (the recoil effect applies to all star wars based weapons and so for this story they are all being downgraded to a realistic damage equivalent).**

 **Next is durasteel, it is again being downgraded due to a post (linked at the bottom of page) which calculates the strength of the alloy using canon material.**

 **The reason I didn't talk about halo during this was because most of the things in halo checks out as science supported (except the halo rings and artificial gravity but the halo rings will be removed and the artificial gravity is also a part of star wars so it's being overlooked)**

 **Links:**

 **threads/durasteel-strength-calcs.109398/**

 **2012/05/star-wars-blaster-speed/**

 **So now on with a summary of how it will work. The idea is that upon first contact the Prophets didn't discover the humans relation to the forerunners and of such didn't declare war, this meant they instead tried to interrogate the humans into the covenant, the UNSC refused due to not trusting the new alien group however they agreed for a trade agreement and beginnings of an alliance. A few months after these events a wormhole opens up at the edge of covenant/human space and is discovered by a Phoenix-class colony ship passing nearby despite the covenant and humans not getting to the point in their alliance where they would share technology they trust each other enough to both send a small force along with colony ships through the wormhole and into an area possibly outside that of communications back home. The wormhole lets out the small force in the star wars galaxy on the edge of the imperial empires owned land in the Unknown regions after colonizing a few planets and setting up a secure communication line (the galaxy's are close enough for the signal to reach it is just delayed) a larger force is sent into the star wars galaxy and a patrol from such force runs into an imperial patrol. This is where our story begins….**


	2. The First Contact

**Chapter 1: The first contact**

 **Before the chapter starts I want to point out this is a star wars AU where the rebels fail the attack on the death star, luke dies and the remaining rebels are swiftly crushed making the imperial Empire the main and completely uncontested force in the star wars galaxy.**

As the combined forces of the UNSC and Covenant scout force moved across a gas giant the captain of the UNSC Dawn could not find anything to quell his boredom, but then again none of his crew could either.

Ever Since the discovery of the portal that led to another galaxy nothing interesting, there had been no signs of life or anything else worth more than a glance, infact now that the captain thought about it nothing major had really had happened back home either, with the help of the covenant most of the insurrectionist groups had been crushed and so nothing interesting seemed to happen anymore.

The relatively small fleet of 3 Paris-class heavy frigates (the captains ship included) and 4 SDV-class heavy corvettes had been set out further into the yet unexplored galaxy than ever before and at first the crew had been excited but now 13 hours in and nothing!

Just as the captain of the UNSC Dawn was about to order the rest of the fleet to slipspace to the next system the ship's onboard scanners picked up the signal of a spacecraft of some kind entering the system a couple kilometers to their right.

Ordering his fleet to hold their position the captain ordered his ship alone to move to intercept the 63 metre long vessel and then to open communications, he did however order the UNSC Dawn's weapons to be readied in case the contact turned out to be hostile, He was upon sending a greeting message met with an unpleasant surprise when the tiny vessel's captain, a man wearing a grey uniform, instead demanded to know who they were and then proceeded to demand their surrender to the Empire immediately after, the UNSC Dawns captain seemingly not threatened by the man's words laughed before asking what such a puny vessel as there's could do, the unknown vessel response was to open fire upon the UNSC Dawn with it's single laser turret.

The plasma rounds did little to the 2 metre thick titanium-A armour of the UNSC Dawn and at once the Captain ordered for a small volley of archer missiles to be fired at the small ship, the archer missiles proved to be overkill as the first missile incinerated the small vessel and all it's crew.

The command deck soon calmed once again as the scanners confirmed no other hostile ships in the area however it held a grim atmosphere at the possibility of a new foe.

"We got a problem on our hands don't we, Gregory" the ship's onboard A.I said to the captain.

"Indeed we do Daniel, Indeed we do" was Gregory's reply to the A.I.

 **And that's a rap! Took a surprising amount of time to write that and I am still sure there is some improvements to be made.**

 **On a side note I need more character names to be used later in the story as I am not an amazing person when coming up with names so if anyone has a name for a character or even a ship that is relevant to the story please send them to me.**

 **Thank you for reading!**


	3. The first stages of war

**The first stages of war**

 **I have too much time on my hands so I decided to do the first two chapters in a row. This one I am hoping will be a bit (a lot) longer and that should be possible since I will just keep adding more and more into this until I have a decent and good sized chapter as I don't have a set ending for this chapter unlike the last chapter.**

The Mobile command base set up on the innermost colony (Cerris 01) was in utter chaos, The reason you might ask? The new information coming from Captain Gregory's patrol fleet was both an exciting yet very scary prospect and so the base was a mess of people coordinating the current land and space faring troops while preparing for the new troops coming from the other side of the portal in an attempt to stop the expected counter attack, obviously many were skeptical that this Empire even knew the location of their colonies as there had been no enemy vessels seen inside the system the UNSC and Covenant had colonized, but still everyone knew this new faction had to be looking for them after what happened and so everyone was preparing anyway.

Another big revelation that had hit the command center was when they watched the clip that the UNSC Dawn's A.I (Daniel) had recorded when they attempted communications with the unknown civilization, and after one of the staff members noticed something odd on the video they re-watched the clip several times and eventually came to the horrifying conclusion, they had fired upon other humans.

It was almost impossible to work out but if you looked closely you could just see the features of a human being. Unfortunately there wasn't much time to dwell on the many questions this brought up as they had to prepare to defend from a possible counter attack the Empire might send in retaliation to destroying what appeared to be one of their scout vessel's, the area of work still held a tense atmosphere because of the many questions swirling through almost everyone's heads about the possibilities of what could happen during this new war.

Either way the best they could do at the moment was prepare their defenses the best they could and evacuate all civilians from the still under construction cities to a more remote location.

On the other side of the planet in orbit Captain Gregory and the rest of his fleet were in the middle of resupplying from a mobile supply ship that had come through the portal a short while after them, unfortunately in the small collection of colonies in the new galaxy their had yet to be a space elevator or space station built meaning all ships had to resupply from mobile supply ships.

Gregory lent back in his chair drinking a coffee as he pondered over the recent events, the current ships nearby consisted of his fleet as well as couple of other Paris classes a handful of Charon classes and then a CCS class, this force would not be able to stand up to any large invasion force so all of their fates was resting on the reinforcements arriving before the expected counter attack did.

The reinforcements supposedly consisted of a marathon class Heavy cruiser, three Halcyon class light cruisers, twelve more Paris Classes, two more CCS classes and finally a CSO class super-carrier.

Everyone hopped this would be enough to fight of any kind of retaliation there new opponent might send.

The vessel they faced was clearly some form of scout vessel that was lightly armored and not meant for combat, which meant there military weapons could be on the level of what the covenant have shown to be able to do which was a very scary thought to both the Captain and his crew.

Before he could continue his thoughts however a message came through from the mobile command base. "Any news on the reinforcements I asked for" Gregory asked immediately before the man on the other end of the call could speak.

"Yes they have arrived through the portal and will meet near on Cerris 05" was the response.

"Have any hostile forces entered the System" Gregory questioned further

"Nothing as of the moment, we haven't detected any unauthorized slip-space jumps nearby".

"Good" Gregory said before cutting the transmission

Cerris 05 was the outermost colony in the solar system they had under their control and was a Ice planet, the planet itself also held the least population and so turned into a kind of military outpost as there were more of their ground troops there than anywhere else in the new galaxy and it was a good place to defend, the Empire would have to go through this planet to get to the inner worlds of the colony and so they would have to take over the icy world, This could take them months just due to the horrible conditions giving the UNSC and Covenant enough time to respond to the threat.

The captain then proceed to send a message to the rest of his fleet to begin to head towards Cerris 04 before ordering Daniel to set the course for said planet immediately.

Upon coming out of slip-space the captain of the UNSC Dawn was surprised to see a battle already underway over the planet's surface, the reinforcement fleet against the expected retaliation fleet. But how? Just 5 minutes ago command said they detected no unauthorized slip-space jumps within their sensor range so how come they had got here without being detected and more importantly how did they know the location of their colonies, they had destroyed all traces of the ship they ran into so how did they discover where there colonies were so quickly. The captain sighed in frustration as he tried to focus on the battle in front of him.

Luckily it seemed the battle hadn't started that long ago as only a few ships from each side had been destroyed and only minor damages were displayed on the intact ships, from what he could tell the reinforcement fleet had only lost two Paris classes so far while the attacking force had lost a few ships that were over the planet away from the main fleet.

He quickly ordered his fleet to join the battle and to concentrate the fire on the large wedge shaped ships first before focusing on the smaller ships, there were four of the wedge shape ships in total and fifteen other ships in the opposing fleet.

On the ground of the planet however the conditions were worse, the invading troops came out of massive pods that fell from space and while only five of these pods made it to the ground as many had been shot out of the air inside the pods was a mass of white armored troops and 4 two legged walkers for each pod.

Out of the original 20 two legged walkers only five remained, this was because of the thin armour on the vehicle allowing sustained fire from an assault rifle to pierce it, the warthogs and scorpions proved overkill in destroying these vehicles, the problem however came with the white armored infantry, it didn't seem to matter how many they cut down there was always another soldier to take his place and so there opponents were slowly wearing away at their defences.

At the moment their right flank was on the verge of collapse and the rest of their defensive positions weren't far of that situation either. Even worse after this the only remaining troops close enough to help was the ones inside the city and they would soon be overwhelmed if this position fell, either way it was clear to him and everyone else that they needed reinforcements and they needed them now.

Back up in space things were a lot less grim, the majority of the invading fleet was destroyed at this point with only one of the wedge shaped ships left as well as few smaller ships, it had cost them however the majority of the Paris class heavy frigates, one CCS class battle-cruiser, a few SDV class heavy corvettes and one Halcyon class light cruiser.

The captain of the UNSC Dawn smiled as the last wedge shaped ship exploded after the bridge and hull had taken too much sustained fire, then however that smile turned to a frown as the debris then collided with a nearby Charon class light frigate destroying that ship as well.

Just as the Captain was about to order the destruction of the last remaining enemy ship he received a transmission from the ship he was just about to destroy, assuming they were surrendering he opened the transmission and was shocked to find not a man wearing the grey uniform he had seen before but instead a UNSC marine, it turned out that in the chaos of the battle a pelican had managed to board and kill or capture the ship's crew, quickly overcoming his shock he ordered the rest of the fleet to not engage the ship but to instead escort it back to the inner colonies so it could be searched for information on the Empire

Then realizing he had forgot to do this earlier ordered his ship to drop the ODST's and to send the on-board marines in pelicans to the ground then requested his allies do the same as to reinforce the ground troops (that had been completely neglected till this point)

On the ground the situation got worse, the right flank had completely collapsed with the remaining scorpions and warthogs covering the army troopers as they retreated to the city and the rest of the defensive line were preparing to do the same when the tell tale signs of a pelican was heard above them, this was backed up by a large portion of the white armored troopers falling to the ground in a shower of blood as the pelicans fired there dual 70mm chain guns.

The battle soon turned in the UNSC favor as the pelicans dropped off marines and the ODST's landed and deployed onto the battlefield, the covenant troops were dropped of by spirits, the combined forces of the marines, the covenant and the army troopers soon overwhelming the remaining invaders and ending the first battle of the war with a UNSC and Covenant victory.

 **Thanks for reading the second chapter of my first story! I want to point out that the reason I did the whole capturing the Imperial cruiser was because I needed to progress along the UNSC's knowledge of star wars things, I needed this because as you can tell I am doing this from a UNSC POV while writing in 3rd person and so I can't call the star wars fighting force their actual names without ruining the immersion so this corrects that problem.**


	4. Gathering their bearings

**Gathering their bearings**

 **Here is the next chapter brought to you by the finely not busy guy!**

The mobile command base was abuzz with activity once again, but this time not under the dread of a possible attack but with excitement over the new information recovered from the captured enemy frigate.

While the ship itself contained little information in regard of their new opponent it didn't take long for the engineers searching the ship for information to find out that it was connected to an entire network of transmissions (kind of like the internet) from this with the help of A.I they began to download as much information into the UNSC's local hard drives as possible.

Unfortunately the engineers had underestimated the Imperials capabilities as even though they had managed to steal some information from the Imperials before being found out, it was still a minuscule amount of what was expected to be on the network.

The information gathered consisted of the basic structure of their opponents government and a wide range of information on various ship classes and ground troops. The information on the Empire's government system surprised the UNSC officers both in the base and back in official UNSC/Covenant land because they discovered that the Empire's government was not a council or anything similar to that but instead a form of Military Dictatorship, this was in the eyes of the UNSC/Covenant a horrible idea when trying to control a large scale Empire.

But still pondering on how exactly the Empire survives of such dangerous form of Government was a question for another time as right now they had to prepare for the coming war, it was clear since the first contact that negotiations were not a possibility so the only thing the UNSC and Covenant could do was attempt to crush the Empire before to much damage could be done to their own fleets and civilians.

In light of the recent events the UNSC and Covenant had decided to merge into one force, the USC (United Species Command), this merging of the two civilizations would allow for improvement in cooperation's between the two factions allowing more efficient battle plans and a much closer public relationship between the two factions (which would be needed for the coming war).

With this new alliance the USC began planning to send a large fleet (numbering near a thousand warships) into Imperial land, they were to find Imperial planets destroy any defending forces in orbit and then commit to either ground invasion or glassing of the planet, they were to do this with as many worlds as possible before setting the groundwork's of a defensive border around the area of the captured planets allowing for another slightly smaller fleet to come along and begin colonizing and preparing the defenses on the captured planets.

The first of these two fleets would arrive within a month so until then it was just a matter of repealing any force the Imperials through at them, luckily there had been no engagements since the battle over and on Cerris 05 and the damaged military force their had started to recover from the massive loss taken during their last battle.

An exciting prospect also was there at the idea of the spartan II's that would be arriving with the first fleet, the spartan II had proven vital in the success of removing the insurrectionists off many UNSC worlds and had so become legends among the rest of the UNSC armed forces, even the majority of the Covenant forces would admit their respect for the ferocious super-soldiers.

"Commander!" came a shout from across the room breaking said commander from his thoughts

"Yes" was the commanders curious reply already beginning the walk over to the officer's desk

"We have some unusual reports on the surface of Cerris 03, there are reports of a crashed freighter that seems to be stealing anyone that enters the ship".

"Really?" asked the commander now standing behind the other man.

"Yes, and there has apparently also been reports of screaming on the inside of the ship, presumably from the people who entered".

The captain frowned at that "and have the local military done anything about this?".

"Yes they tried but the squad they sent in but disappeared as well".

"... okay then send a the UNSC Dawn to investigate" said the slightly disturbed captain.

"Roger that" was the officer's final comment before the commander walked away.

Captain Gregory frowned as his break was interrupted by a beep from the monitor next to him, a message. A quick read informed him that an anomaly had appeared on Cerris 03 and that him and his crew were to be sent to investigate, the Captain sighed as he got up and prepared to tell the crew of their new orders.

 **That's the third chapter with a nice little cliffhanger on the end, I will give the first person who can guess what the anomaly is an OC as a spartan in the story as well…. No I am serious, it's kind of obvious what it is (in my mind) so I am sure someone will guess it before the next chapter is written, till then see ya!**


	5. The Infection

_**The Infection**_

 **Hi! It's been a while I realize since my last chapter post and that has been for multiple reasons however I don't exactly want to waste a few minutes of your life explaining the horrors of my life so without further ado, here's the story.**

 **Disclaimer: I do not own either franchise portrayed in this fanfiction or any of the characters (except OC's)**

The UNSC Dawn hovered over Cerris 03, the marines that had been deployed to the planet's surface hours ago had yet to report back to the ship, this greatly worried the crew and everything on the bridge was tense. Captain Gregory was currently preparing to send a more numerous and heavily armed force to the surface to investigate the mysterious event, curiously several nearby settlements had also cut communications and Gregory had already warned the commanding officer of Cerris 03's defending army of these strange events, with the rate the problem seemed to be spreading it may pose a significant threat to the planets populous and more importantly the efforts put into dealing with the Galactic Empire and its associates.

4 Pelicans boosted out of the hangers of the Frigate, all were packed full of marines and two carried vehicles, one scorpion and one warthog, two of these were going directly to the crash site and two were heading towards a city that had cut communications with the UNSC Dawn. a certain sergeant named William was nervous, he was in one of the pelicans heading for the crash site and while the incident had only happened a few days ago many rumors had already spread among the crew, many blamed it on their new enemies the Empire and some even called out the covenant saying they were trying to weaken them. William could only hope that this didn't turn out horribly.

Two Pelicans settled down near the wrecked corpse of the UNSC cargo freighter quickly depositing their occupants before taking off to redock with the UNSC Dawn, from his perspective William could see blood stains on the ground outside the destroyed ship these were clearly from the poor souls who investigated the crash site soon after it crashed, the question of where the bodies went was a clear mystery to him and his squad however the lack of bodies and their killers on the exterior of the ship made on unfortunate thing clear. They would have to enter the ship, this is something williams had been dreading ever since he heard he had been assigned this mission and hours on he was still not looking forward to it. Despite his fears he ordered his squad forward the second squad following behind them.

They reached the doors and entered soon after, at first things seemed fine other than more blood stains the ship seemed mostly normal, well if you ignore the damage done by the crash the ship seemed normal, it was only when the reached the heart of the vessel, the room they entered looked like a battle ground, bullet holes skewered the walls and sandbags along with many other miscellaneous objects scattered the room. To William this looked like the area where the crew took there last stand and if the numerous blood stains and torn limbs was any indication they had failed their objectives. Williams line of thought was broken however when a curious creature crawled down from the wall and within a moment all eyes in the room were on it, they hesitated however as the little creature looked to be of no harm. This hesitation however cost them as the second the petite animal was close enough it lashed out at the nearest marine embedding itself into his chest, despite the best efforts of the rest of the man's squad by the time the creature was removed and killed he was already dead more of the monstrosities entered the room through passages and the room was lit up almost instantly by gunfire, despite the pure volume of bullets many of the creatures made it through and by the time the order to retreat was given five men had already been lost to the infection, they ran and ran through many corridors and rooms, spurred on by the screams of their comrades as they were chased down and picked off one by one. William exited the carcass of the freighter in a mad dash and he along with the remaining marines didn't stop running for several more minutes. When they did stop running only a few of the past hordes of monstrosities remained and these were easy to deal with, after they were dealt with William looked around at the two remaining marines, both were just as panicked as he was and he knew he needed to do something, since he had no idea of his location and he only had a radio on him, he would contact the UNSC Dawn and then head to the nearest city to see if anyone there was still alive.

 **That's the fourth chapter, it took awhile to make I don't have time to check it has much as I normally do so I apologize for any mistakes in advance, come back next chapter to learn the fate of the other marines and find out what happens to william and his remaining squad.**


	6. Desperation of Cerris 03

**_Desperation of Cerris 03_**

 ** _I am back! For the next chapter of this story. Firstly since I am a man of my word, to the person that correctly guessed the cause of the problem of the problems on Cerris 03 send me a pm… If you can through a guest account. If your can't leave another review detailing the character or create an account and send me a pm. Now, on with the chapter!_**

Two Pelicans soared over the desolate streets of one of the nameless cities of Cerris 03, the Pelicans slowed in their flight before circling round and lowering down onto a relatively clear spot on a road. First a scorpion and warthog dropped to the ground then the squads of marines poured out of the overpacked Pelicans onto the concrete road below. The two vehicles were quickly manned and the Pelicans returned to the sky, they would no longer be needed.

With the slight chaos of the disembarking over, the marines deployed could finally get a close look at the streets of one of the many cities that had for some reason cut reason communications . They were deserted with nothing but the occasional parked or crashed car at first glance, however once you looked carefully you could see bullet holes, in roads and walls, bloodstains scattered occasionally everywhere and the occasional damaged glass sheet. Curiously not a single body or anything to indicate a battle (besides the damage done was left behind) could be found. In spite of this the team continued onwards down the street, they had a mission to complete after all. There mission? To find out the cause of the weird happens in the city, either through survivors or direct contact with the source of the problem and if said problem proved hostile they were to try to eliminate it before reporting back for reinforcements from the planets ground side soldiers and were then to attempt to remove all remaining hostiles on the planet.

Nothing at all was found during the first few hours of searching except the usual bloodstains and damaged cars and buildings when the group happened upon a surprisingly large building. Their ships A.I quickly informed them that this was a ONI building and while on the outside the five story office building was in no way impressive the inside was another story, not only did it look a lot bigger on the inside but there was also 8 floors underneath the building with another 12 underground floors being planned in the near future. The ONI building was made like this so to not draw suspicion from their new enemies the Galactic Empire. The power to this area of the city had been cut so the inside of the building was pitch black, 7 marines were ordered to clear the building and so entered into the building with flashlights and night vision equipment on. The scary part was, that once you entered the underground area of the building the radios that the marines carried would not work and anything including the sound of bullets being fired could not be heard, so once they got underground they were on their own.

It had been nearly 30 minutes since the marines reported that they were about to enter the underground section of the ONI building and since then nothing had happened, no reports through the radio and no sight of the seven marines sent into the building. This was odd as the team cleared all the surface floors in a significantly shorter amount of time, as was expected the marines left on the surface were beyond nervous and were liable to panicke at any moment. The sergeant in charge was getting more and more anxious waiting for the team to show up, several more minutes passed by in an uncomfortable silence eventually the sergeant decided that something was needed to be done, if only to calm the men's nerves, four more marines were sent forward including the sergeant and three privates.

The four paced into the building flashlights blazing and ready for whatever was down below, they made their way to the stairs. Entering the vertical passageway they clambered down the countless rows of stairs, they didn't make it far however as after just reaching the first underground floor they heard a scream, not from where they were about to enter but from in the shaft with them, more specifically, behind them.

William walked cautiously through the barren streets of a some city with his two fellow marines following close behind him, despite hours of searching they had yet to find anything useful and at first coming across the city looked promising. Cheers had been shared upon seeing the cluster of buildings in the distance, yet after getting closer to the unbenounced to them ruined city it was clear through the scattered vehicles bloodstains and bullet holes that they had been here before them. In spite of this haunting knowledge the small team pressed forward hopping for survivors, supplies or possibly even running into the other teams put onto the ground. Nothing happened at first with nothing being found at all until suddenly a foul screech sounded behind them, the team didn't need to look as they already knew what it was. The monstrosities had found them.

The three men didn't need anymore prompting, the second they were facing the infection form the little thing was met with a hail of bullets. Many more infection forms jumped out of buildings and made their way towards the marines, another wave of bullets incinerated the majority of these. The rest of the visible flood forms were easy to destroy, the scared marines couldn't celebrate their minor victory as another bullet storm approached them this time from a mutated humanoid figure carrying a UNSC smg, William was injured being shot twice in his left leg, the marine to his left however was not so lucky 8 bullet holes mostly near vital places appeared on his body, he was dead before he hit the floor. William felt a great pain begin to accompany his wounds and the last thing he saw before passing out was the mutated humanoid collapsing as his other teammate unloaded his clip into it.

 ** _That's it for this chapter, can't really fit anything more in without ruining the suspense so see ya next time!_**


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